This proposal is to request support for a Keystone Symposia meeting entitled "Prevention of HIV/AIDS," organized by Brigitte Autran and Scott M. Hammer, which will be held in Keystone, Colorado from March 22 - 27, 2009. Most recent research efforts on the prevention of HIV and AIDS have focused on T cell-based vaccines but this approach has recently suffered setbacks and clearly will benefit from novel approaches, such as renewed efforts to generate HIV neutralizing antibodies. The lessons learned from recent successes and failures with alternative methods of HIV prevention (e.g., microbicides, circumcision) as well as alternative approaches to AIDS prevention (therapeutic vaccines) should help us better understand how to develop and implement HIV vaccines. However, maximizing the potential for such advances requires sharing basic understanding and results among investigators in the different fields. Indeed, the recent negative results of a major HIV vaccine trial have substantially perturbed the field of prophylactic vaccines, and provide compelling arguments for enhanced interactions among investigators with a wide variety of perspectives. The Prevention of HIV/AIDS meeting is designed to foster this much needed sharing and interaction. The goals of the Prevention of HIV/AIDS meeting are therefore to focus on the most recent key advances in the understanding of (1) how HIV can be controlled at entry and after infection (to be discussed in three joint sessions with the concurrent HIV Immunobiology: From Infection to Immune Control meeting);(2) how T cell- based or antibody-based HIV vaccines can be improved;and (3) results from current vaccine trials and from alternative methods of HIV or AIDS prevention and how can they help at re-orientating vaccine research. Two workshops will provide key information regarding immune correlates of protection and their analysis in clinical trials. The field of HIV prevention is going through a period of significant reflection and discussion regarding priorities and approaches. The Keystone Symposia meeting on Prevention of HIV/AIDS brings together leading experts in a variety of fields for in-depth interdisciplinary discussions regarding recent advances in novel vaccine and other preventive approaches.